Method for Operating a Washing Machine

ABSTRACT

A method for operating a washing machine includes cyclically reading values detected by a sensor for detecting a weight of a washing assembly container of the washing machine. At least a last read value of the read values is stored. A rest position of the container is determined as long as the read values are below a predetermined tolerance level. The control unit is activated when a read value of the read values exceeds the predetermined tolerance level.

CROSS REFERENCE TO PRIOR APPLICATION

This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/EP2005/009509, filed Sep. 5, 2005, and claims benefit of German Patent Application No. 10 2004 043 838.2, filed Sep. 8, 2004, which is incorporated by reference herein. The International Application was published in German on Mar. 16, 2006 as WO 2006/027183 A1 under PCT Article 21(2).

The present invention relates to a method for operating a washing machine and, in particular, to a method for a program-controlled washing machine including a housing, a washing assembly which is resiliently mounted in the housing and includes a container for receiving laundry and/or wash liquid, the washing machine further including a control panel and a control unit, the control unit including at least one evaluation unit and a memory, and the washing machine further including a sensor for detecting the weight of the container.

BACKGROUND

German Utility Model Patent DE 298 12 393 describes a washing machine including an oscillating washing assembly and a force or pressure sensor provided on one of the suspension means of the washing assembly for weight measurement purposes.

Another way of detecting the weight is disclosed in German Laid Open Application DE 199 60 847 A1 and consists in providing a strain gauge in the area of the rear wall of the suds container, said strain gauge changing its electrical properties in response to twisting of the holding members of the drum. The load condition of the drum is thus determined based on the measured electrical properties. In this method, the measurement is limited to the content of the drum, so that it is not possible to measure the weight of the wash liquid contained in the suds container.

German Laid Open Application DE 101 22 749 A1 describes a washing machine which includes an oscillating washing assembly and uses a displacement sensor to determine the weight. The washing assembly is suspendedly mounted to the housing by means of springs, and uses shock absorbers in the form of friction dampers, or so-called spring plunger-type friction dampers. Also described therein is a displacement sensor which is incorporated in a spring plunger-type friction damper.

In all of the known systems for detecting the weight of the laundry, it is mandatory, first of all, that the control unit, or the detection means, be activated prior to introducing the laundry into the washing drum, said activation generally being effected by turning on the washing machine. However, if the laundry is introduced into the washing drum prior to turning on the washing machine, it is no longer possible to automatically detect the laundry weight because the rest position of the washing drum, or of the washing assembly, is not known.

In this regard, German Laid Open Application DE 102 36 937 A1 describes a way to automatically activate or turn on the control panel of a washing machine. In that patent, the control panel is activated by an integrated motion detector. The indicators located in the control panel or the control unit are not activated or turned on before a person is present in the area covered by the motion sensor. However, the use of a motion sensor is very complex and sensitive to unwanted activation.

Another way of detecting the laundry weight in washing machines is described in German Patent DE 198 47 487 C2. In that patent, both the recovery behavior of friction-based shock absorbers and the different user habits are taken into account. The rest position of the washing assembly prior to introducing the laundry for a new wash cycle is determined after turning on the washing machine and taken into account in the determination of the weight after the laundry is introduced. In the event of erroneous control inputs, or when laundry is introduced prior to turning on the washing machine, the detection unit detects a value outside the tolerance range for the rest position, and a rest position determined in the last wash cycle is taken into account by the detection unit in this weight determination procedure. This has the disadvantage that if the user has this habit, a slow change in the rest position resulting from wear of the suspension means or shock absorbers is not detected and therefore not taken into account in the determination of the weight.

SUMMARY

It is therefore an object of the present invention, on the one hand, to enable the weight of the laundry and/or of the loaded container to be detected reliably and accurately, while taking into account different user habits and, on the other hand, to enable disturbances to be detected before the program is started.

The present invention provides a method for operating a washing machine. The washing machine includes a housing, a washing assembly resiliently mounted in the housing and including a container for receiving laundry and/or wash liquid, a control panel, a control unit including at least one evaluation unit and a memory, and a sensor for detecting a weight of the container. The method includes: cyclically reading values detected by the sensor;

storing at least a last read value of the read values;

determining a rest position of the container as long as the read values are below a predetermined tolerance level; and

activating the control unit when a read value of the read values exceeds the predetermined tolerance level.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention is shown in the drawings in a schematic way and will be described in more detail below. In the drawings,

FIG. 1 a schematically illustrates the arrangement of the washing assembly in a housing;

FIG. 1 b schematically illustrates the position of the washing assembly in a loaded condition;

FIG. 2 shows, by way of example, a state diagram for the control;

FIG. 3 a shows a time history for an introduction of laundry;

FIG. 3 b shows a time history for an improper entry of water.

DETAILED DESCRIPTION

In addition to a reliable and accurate determination of the laundry weight while detecting and accounting for disturbances, another advantage made possible by the present invention is the reliable activation of the control panel and/or the control unit. An example of a disturbance to be mentioned is the recovery behavior of friction-based shock absorbers. Because of the frictional behavior, the unit to be measured reaches a slightly different position each time it is reset when the decelerating effect of the friction-based shock absorber dominates over the restoring force of the springs used for the resilient suspension of the washing assembly. After a spin-dry cycle at the end of a wash program, the rest position may differ considerably because of the imbalance-induced vibrations of the washing assembly or of the container. Another disturbance is an improper entry of water into the container, for example, into the suds container.

In order to achieve these advantages, the rest position of the container or washing assembly receiving the laundry and/or the wash liquid is reliably determined shortly before each wash cycle. This provides the advantage that changes in the weight of the container are detected and evaluated before the wash program selected by the user is activated. To this end, a control unit including an evaluation unit and a memory, and a sensor for detecting the weight are provided in the washing machine. The values detected by the sensor are cyclically read in, and at least the last read value is stored. This allows the evaluation unit to compare a read value to the last value read or a plurality of values. As long as the values read do not change or fall below a predetermined tolerance level, the rest position or home position of the container, generally the washing assembly, will be determined. When a read value exceeds the predetermined tolerance level for a change in value, the control unit will be activated.

In a suitable embodiment, a displacement sensor is used for detecting the weight, said displacement sensor generally being disposed between the washing assembly and the housing. The laundry weight can also be detected using other methods, such as by pressure measurement or twist measurement.

In another advantageous embodiment, the variation with time of a plurality of stored values is used for evaluation.

In order to obtain an accurate result, the displacement sensor is read at least one more time after the control unit has been activated, and from this value, which is read under load, is subtracted the value that was detected for the rest position in the sleep mode, and the result of this calculation is used as the weight of the laundry. In order to minimize inaccuracies in the value of the rest position, it is possible to insert delays between the individual sensor value acquisition cycles, or to perform a plausibility check based on a plurality of consecutively acquired values. This means, for example, that a constant value is assumed to be the rest position only after several successive measurements have been made.

Since the method of the present invention detects and evaluates the weight of the washing assembly or of the container for receiving laundry and/or wash liquid, the method is suitable for all washing machines that have a resiliently suspended washing assembly, in particular a suds container, a washing drum rotating therein, and the drive components of said washing drum; or a tub, an agitator disposed therein, and the drive components of said agitator; or a water-filled rotating drum and its drive components. Due to the recovery behavior of the friction dampers, the determined or assumed rest position may be within a defined tolerance range.

The determination of the rest position is carried out during the time in which the control panel and the control unit are inactive, i.e., when all controls are inactive and the indicators, such as indicator lights and displays, are turned off. During this time, the control unit is inactive, which is hereinafter referred to as “sleep mode”, except for the cyclic acquisition and storage of the values from the displacement sensor. This sleep mode is particularly energy-efficient because only part of the control unit or evaluation unit is active.

In an advantageous embodiment, the cyclic detection of the weight of the container or washing assembly makes it possible to detect faults, in particular an improper entry of water in the sleep mode, i.e., while the washing machine is turned off or the control unit and the control panel are inactive. For this purpose, the dynamic behavior of the values read from the sensor is taken into account. If the change of a read value as compared to the previously stored value is below a predetermined level, this is evaluated as a slow increase in weight resulting from an improper entry of water. Once a further predetermined threshold is exceeded, the evaluation unit will detect a fault and activate an alarm function. Possible alarm functions advantageously include visual alarm indications, audible alarm indications, or alarm signaling via communication systems such as the Internet, mobile telephone, and/or activation of the drain pump for removing suds.

As schematically shown in FIG. 1, washing assembly 2 is resiliently mounted by springs 3, in a suspended fashion, to housing 1, or to load-bearing parts (not further described) of the housing. The washing assembly essentially includes a suds container, a washing drum rotatably mounted in said suds container, and the drive system, for example, a motor with a belt drive. Shock absorbers 4 are used to prevent vibrations in the event of an imbalance of the rotating drum. A displacement sensor 6 is used to detect imbalance and, in addition, the load condition of the drum. The values output by or read from displacement sensor 6 are preferably evaluated in a control unit 5 which is disposed in washing machine 29 and includes at least one evaluation unit and a memory. The washing assembly 2 schematically shown in FIG. 1 a is in an unloaded condition, while the schematic view of FIG. 1 b shows washing assembly 2 in a loaded condition. Here it can clearly be seen that washing assembly 2 is in a appreciably lower position as compared to its rest position 8, so that displacement sensor 6 outputs a value that corresponds to a high weight of washing assembly 2. Control unit 5 includes an evaluation unit which reads each value of displacement sensor 6 via signal connection 7 and interprets a value change corresponding to a change in the weight of washing assembly 2 as the weight of the laundry. In the process, the evaluation unit distinguishes the dynamic behavior of the weight change, one function being the automatic activation of washing machine 29 or control unit 5.

As illustrated in a state diagram in FIG. 2, no state transition occurs as long as the detected value s(t) does not differ from one or more values s(t−n) detected at previous points in time, or is below a predetermined tolerance limit 18, i.e., control unit 2 remains in sleep mode 9. The state diagram of FIG. 2 further shows that control unit 2 is switched from sleep mode 9 to active mode 10 as a function of the values s(t) 14 output by displacement sensor 6, in particular when a currently detected value s(t) of one or more values s(t−n) detected at previous points in time is greater than a predetermined tolerance limit, or corresponds to a higher weight of washing assembly 2; thus, a state change 11 takes place. In active mode 10, for example, the control panel is activated along with the indicators, and control unit 5 is made ready to receive control inputs. It should be noted here that in the sleep mode, the energy consumption of the entire washing machine is appreciably below an established threshold for a relevant level of energy consumption in the to-be-provided sleep mode, generally also referred to as “standby”. A transition change 13 from active mode 10 to sleep mode 9 can occur depending on the progression of the wash program or other actions of the user, such as terminating the wash program, opening the door and removing the laundry.

FIG. 3 a shows, by way of example, the dynamic behavior over time for an introduction of laundry, and the state changes resulting therefrom. The value of displacement sensor 6 is cyclically read at intervals in time. The instants at which the displacement sensor is read out are exemplarily indicated on time axis t by 1 through 15. The read, low value 15 remains unchanged until instant 10. This read value 15 is stored as a reference for the rest position 15 or home position of the washing assembly, preferably in a memory within control unit 5. At instant 11, the read value exceeds a predetermined tolerance level 18, whereupon the evaluation unit in control unit 5 detects an introduction of laundry at state 16 and switches the control unit 5 and the control panel from sleep mode 9 to active mode 10, as illustrated by transition arrow 19. When the final value 17 is reached, this value 17 is taken for determining the laundry weight. The weight of the laundry is determined based on this value 17 minus the previously determined value for rest position 15 of washing assembly 2.

FIG. 3 b illustrates another way in which the evaluation unit, based on the cyclic acquisition of the value of a displacement sensor 6, can detect an improper entry of water into the washing assembly and subsequently activate an alarm function 26. An improper entry of water would cause a slow increase in the weight of the suds container and, consequently, of washing assembly 2. This would lead to changes in value over time, each individual detected change in value being below a predetermined level 28. The evaluation unit will only detect a fault if the detected change in value is below a predetermined level 28 and the last detected value exceeds a predetermined absolute threshold 20. At instants 1 and 2, no change 20 is detected in the read and/or stored values 15. At the instants t=3 through t=5, a change 20 is detected in the read and/or stored values, but the values are below a threshold 20 for fault detection. At instants 6 through 7, an increased small change 21 is detected in the read and/or stored values, said change being just at the threshold 20 for fault detection. At instants 8 through 10, an increased change 22 is detected in the read and/or stored value, which are above the threshold 20 for fault detection and continue to increase 23 after the instant 10. Since each change in value 27 is below the predetermined level 28, the variation with time of the value change, together with the exceeding of threshold 20, is interpreted by evaluation unit 5 as an improper entry of water, whereupon the evaluation unit can activate an alarm function 26. As illustrated in FIG. 1 a, alarm function 26 may be an audible alarm indication 31, visual alarm indication 30, or alarm signals transmitted via data-transmission media 32, or activation of drain pump 33 for removing suds, in order to prevent water damage by water leaking from washing assembly 2.

The present invention is not limited to the embodiments described herein; reference should be had to the appended claims.

LIST OF REFERENCE NUMERALS

-   1 housing -   2 washing assembly -   3 spring -   4 shock absorber -   5 control panel and/or control unit -   6 displacement sensor -   7 signal connection -   8 rest position -   9 sleep mode -   10 active mode -   11 transition to the active mode -   12 continuance of the sleep mode -   13 transition to the sleep mode -   14 reading cycle -   15 displacement sensor in the rest position -   16 displacement sensor detects introduction of laundry -   17 displacement sensor detects final laundry weight -   18 tolerance level or threshold for load detection -   19 transition arrow -   20 threshold for fault detection -   21 value<threshold -   22 value=threshold -   23 value>threshold -   24 value>>threshold -   25 alarm function deactivated -   26 alarm function activated -   27 change in value -   28 predetermined level for the change in value -   29 washing machine -   30 visual alarm function -   31 audible alarm function -   32 communication system -   33 drain pump for removing suds 

1-6. (canceled)
 7. A method for operating a washing machine comprising a housing, a washing assembly resiliently mounted in the housing and including a container for receiving laundry and/or wash liquid, a control panel, a control unit including at least one evaluation unit and a memory, and a sensor for detecting a weight of the container, the method comprising: cyclically reading values detected by the sensor; storing at least a last read value of the read values; determining a rest position of the container as long as the read values are below a predetermined tolerance level; and activating the control unit when a read value of the read values exceeds the predetermined tolerance level.
 8. The method as recited in claim 7 wherein the sensor includes a displacement sensor.
 9. The method as recited in claim 7 further comprising evaluating, using the evaluation unit, a variation over time of changes in the read values.
 10. The method as recited in claim 8 further comprising evaluating, using the evaluation unit, a variation over time of changes in the read values.
 11. The method as recited in claim 7 further comprising determining, using the evaluation unit, a laundry weight based on a final read value of the read values minus a value of the read values for a rest position of the washing assembly.
 12. The method as recited in claim 7 further comprising detecting, using the evaluation unit, a fault, and activating, using the evaluation unit, an alarm function, when a change in the read values is below a second predetermined level and at least a last read value of the read values exceeds a predetermined threshold.
 13. The method as recited in claim 12 wherein the fault includes an improper entry of water.
 14. The method as recited in claim 12 wherein the alarm function includes at least one of a visual alarm indication, an audible alarm indication, an alarm signaling via a communication system, and an activation of a drain pump for removing suds. 